CN113173787B - Gadolinium zirconate/gadolinium tantalate composite ceramic and preparation method thereof - Google Patents
Gadolinium zirconate/gadolinium tantalate composite ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of inorganic non-high temperature composite ceramic materials, and particularly relates to gadolinium zirconate/gadolinium tantalate composite ceramic and a preparation method thereof. The raw materials used by the ceramic are gadolinium oxide, zirconium oxide and tantalum oxide, composite raw materials of gadolinium zirconate and gadolinium tantalate are respectively prepared, the raw materials are weighed according to a proportion, the prepared raw materials are mixed in absolute ethyl alcohol and then placed in a planetary ball mill for ball milling, so that the raw materials can be uniformly mixed, and the mixed powder is dried and then sintered; and cooling, taking out sintered gadolinium zirconate and gadolinium tantalate samples, grinding, weighing according to a composite ratio, ball-milling, drying, placing dried powder in a mold, compacting, and sintering. The invention has high process purity, low impurity content and low product preparation cost, is suitable for batch production, and the target product has good thermophysical property and is expected to be used as a novel high-temperature-resistant, oxidation-resistant, corrosion-resistant and anti-ceramic material.
Description
Technical Field
The invention belongs to the technical field of inorganic non-high temperature composite ceramic materials, and particularly relates to gadolinium zirconate/gadolinium tantalate composite ceramic and a preparation method thereof.
Background
The chemical formula of the rare earth gadolinium zirconate is Gd 2 Zr 2 O 7 Compared with the traditional 8 YSZ, the rare earth gadolinium zirconate crystal structure has higher oxygen vacancy concentration, increases phonon scattering and has lower thermal conductivity (1.390 Wm) -1 K -1 1373K), in addition, rare earth zirconates have higher melting points, better high temperature phase stability, higher thermal expansion coefficient (10.400 × 10) -6 K -1 1473K) and the like, and is regarded as a ceramic layer material of a thermal barrier coating with a good application prospect. However, gadolinium zirconate has a lower coefficient of thermal expansion than conventional thermal barrier coatings, resulting in a lower thermal cycle life. Wang Caimei (university of Tianjin, 2017) and the like effectively increase the fracture toughness of the material by introducing lanthanum phosphate as a second phase to gadolinium zirconate, but the effect on the thermal expansion coefficient is not mentioned.
Research shows that the rare earth gadolinium tantalate has higher use temperature (1600 ℃) and higher heatCoefficient of expansion (11.021 × 10 -6 K -1 1273K), better high-temperature phase stability and phase transition into second-order phase transition (from M phase to T phase at 1450 ℃), and a ferromagnetic crystal structure, so that gadolinium tantalate can be used as a second phase to improve the thermal physical properties and the mechanical properties of gadolinium zirconate.
The current methods for preparing thermal barrier coating materials include solid phase synthesis, sol-gel method, coprecipitation method and the like. The solid phase synthesis method is a more traditional method, and the high temperature synthesis steps are generally divided into material preparation, ball milling, sieving, press forming, calcining and product production. The solid phase method has simple process, low cost and good operability, and is beneficial to production and application; however, the sample powder obtained by the conventional solid-phase reaction has disadvantages of non-uniform microstructure, easy introduction of foreign impurities, segregation of components, and the like. The sol-gel method is a hydrolysis reaction and a condensation reaction, compounds with higher chemical activity are uniformly mixed, then a chemical reaction is carried out by taking water as a medium, a transparent sol system is formed in a solution, and the sol is aged to form gel, dried, calcined and solidified to obtain the final nano-scale powder. The method for preparing the powder has the advantages of simple equipment, controllable and adjustable process, small particle size and high purity of the product, uniform distribution and low sintering temperature. But the experimental period is long, the cost is high, and fine powder is easy to agglomerate. The coprecipitation method is a method that the reactants mixed according to the proportion are prepared into solution, precipitator is added into the solution, then the supernatant fluid is filtered, deionized water or absolute ethyl alcohol is used for washing the precipitate, then the precipitate is dried and heated and decomposed to obtain the required powder. The coprecipitation method is simple and easy to operate, the sintering temperature is low, the reaction condition is easy to control, and the cost is low. The disadvantages are that the precipitate is easy to agglomerate in the washing, filtering and drying processes to enlarge the particle diameter of the powder and have poor dispersibility. The invention uses solid phase synthesis method, and pure ceramic material can be obtained by secondary sintering.
Disclosure of Invention
The invention aims to provide a preparation method of gadolinium zirconate/gadolinium tantalate composite ceramic, which overcomes the defects of the traditional method, has high purity and low preparation cost, is suitable for batch production, and has better thermal property and mechanical property.
The invention adopts the technical scheme that a preparation method of gadolinium zirconate/gadolinium tantalate composite ceramic comprises the following steps:
1) Weighing gadolinium oxide and zirconium oxide according to a proportion to prepare gadolinium zirconate;
2) Mixing the weighed raw materials of gadolinium oxide and zirconium oxide in absolute ethyl alcohol, and then placing the mixture into a planetary ball mill for ball milling to ensure that the raw materials can be uniformly mixed;
3) Drying the mixed powder;
4) Pre-sintering the dried powder; and cooling, taking out the pre-sintered sample, grinding, ball-milling and drying, and sintering the dried powder for the second time to obtain the gadolinium zirconate powder material.
5) Weighing gadolinium oxide and tantalum oxide according to a proportion to prepare gadolinium tantalate;
6) Ball-milling and drying the weighed raw materials of gadolinium oxide and tantalum oxide, and sintering the dried powder to obtain gadolinium tantalate;
7) Weighing gadolinium zirconate and gadolinium tantalate according to the proportion to prepare gadolinium zirconate/gadolinium tantalate composite ceramic;
8) Ball-milling, drying and sieving the weighed gadolinium zirconate powder and gadolinium tantalate powder, placing the sieved powder in a die for compacting, and then sintering.
Further, in the step 1), the molar ratio of the gadolinium oxide to the zirconium oxide is 1:2.
Further, in the step 2), the rotating speed of the ball mill is 120r/min, and the ball milling time is 12-13 h.
Further, in the step 3), the drying temperature is room temperature, and the drying time is 15-24 hours.
Further, in the step 4), the pre-sintering temperature is 1400 ℃, the secondary sintering temperature is 1400 ℃, and the sintering heat preservation time is 6 hours.
Further, in the step 5), the molar ratio of the tantalum oxide to the gadolinium oxide is 1:1.
Further, in the step 6), the sintering temperature is 1500 ℃, and the heat preservation time is 6 hours.
Further, in the step 7), the molar ratio of the gadolinium zirconate to the gadolinium tantalate is 9:1-1:9.
Further, in the step 8), the sieving refers to sieving by a 200-300-mesh sieve; and when the powder is pressed, the pressure maintaining pressure is 30-40 Mpa, and the pressure maintaining time is 1min.
Further, in the step 8), the sintering temperature is 1400-1600 ℃, and the calcination time is 6h.
The gadolinium zirconate/gadolinium tantalate composite ceramic is obtained by the method, and has the chemical formula of (Gd) 2 Zr 2 O 7 ) 1-x /(GdTaO 4 ) x And x is more than or equal to 0.1 and less than or equal to 0.9, namely the molar ratio of the gadolinium zirconate to the gadolinium tantalate is 9:1-1:9. The invention has the beneficial effects that:
(1) After the powder is mixed by the secondary ball mill, the powder can be uniformly mixed, so that the powder can fully react during secondary calcination.
(2) High process purity, low impurity content, low product preparation cost and suitability for batch production.
(3) The prepared gadolinium zirconate/gadolinium tantalate composite ceramic has low thermal conductivity which can reach 0.920W/(m.K) at 800 ℃, high thermal expansion coefficient and reach 11.741 x 10 at 1400 DEG C -6 K -1 And is expected to be used as a novel high-temperature ceramic material.
(4) The prepared gadolinium zirconate/gadolinium tantalate composite ceramic has a ferroelastocrystal structure and high-temperature phase stability.
(5) Compared with pure gadolinium zirconate, the prepared gadolinium zirconate/gadolinium tantalate composite ceramic has better mechanical property and thermal property.
Drawings
FIG. 1 is an XRD pattern of a gadolinium zirconate ceramic powder obtained in preparation example 1 of a gadolinium zirconate/gadolinium tantalate composite ceramic according to the present invention.
FIG. 2 is an XRD pattern of gadolinium tantalate ceramic powder obtained in preparation example 1 of gadolinium zirconate/gadolinium tantalate composite ceramic of the present invention.
FIG. 3 is an XRD pattern of bulk gadolinium zirconate/gadolinium tantalate ceramic obtained in preparation examples 1, 2 and 3 of gadolinium zirconate/gadolinium tantalate composite ceramic of the present invention.
FIG. 4 is a thermal diagram of a gadolinium zirconate/gadolinium tantalate ceramic block obtained in preparation examples 1, 2 and 3 of a gadolinium zirconate/gadolinium tantalate composite ceramic of the present invention.
FIG. 5 is a thermal expansion coefficient diagram of a gadolinium zirconate/gadolinium tantalate ceramic block obtained in production examples 1, 2 and 3 of a gadolinium zirconate/gadolinium tantalate composite ceramic of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following embodiments.
Example 1
The embodiment of the invention provides a novel gadolinium zirconate/gadolinium tantalate composite ceramic material with high temperature resistance, low thermal conductivity and high thermal expansion coefficient and a preparation method thereof, and the preparation method specifically comprises the following steps:
weighing 29.763g of gadolinium oxide and 20.227g of zirconium oxide, pouring into 250ml of absolute ethyl alcohol, mixing, placing in a planetary ball mill for ball milling (the ball milling rotating speed is 120r/min, the ball milling time is 13 h), drying the ball-milled suspension for 24h at room temperature, placing in a high-temperature furnace, and preserving the heat of 6h at 1400 ℃ in the air atmosphere to obtain the pre-sintered gadolinium zirconate powder material.
Fully grinding the powder material obtained by the first calcination, pouring into 250ml of absolute ethyl alcohol again, mixing, placing in a planetary ball mill for ball milling (the ball milling rotation speed is 120r/min, the ball milling time is 13 h), drying the ball-milled suspension at room temperature for 24h, placing in a high-temperature furnace, preserving heat for 6h at 1400 ℃ in the air atmosphere, and uniformly grinding the calcined material to obtain the pure gadolinium zirconate powder material.
Weighing 36.255g of gadolinium oxide and 44.175g of tantalum oxide, dividing into 4 parts, pouring into 200ml of absolute ethyl alcohol, mixing, placing into a planetary ball mill for ball milling (the ball milling rotation speed is 120r/min, the ball milling time is 13 h), drying the ball-milled suspension at room temperature for 20h, calcining and sintering at 1500 ℃ in a high-temperature furnace, keeping the temperature for 6h, and grinding the calcined material uniformly to obtain the pure gadolinium tantalate powder material.
Weighing 16.436g of gadolinium zirconate powder material and 1.214g of gadolinium tantalate powder material, pouring the weighed materials into 200ml of absolute ethyl alcohol, mixing, placing the mixture into a planetary ball mill for ball milling (the ball milling rotation speed is 120r/min, the ball milling time is 13 h), drying the ball-milled suspension for 20h at room temperature, sieving the ball-milled suspension by a 200-mesh sieve to obtain powder, placing the obtained powder into a die with the diameter of 15mm for press molding, wherein the pressure is 30Mpa, and the pressure maintaining time is 1min. And then placing the obtained molded original sheet into a high-temperature furnace, and preserving heat for 6 hours at 1500 ℃ in the air atmosphere to obtain the gadolinium zirconate/gadolinium tantalate composite ceramic material.
Performing an XRD test on the gadolinium zirconate powder material, the gadolinium tantalate powder material, and the gadolinium zirconate/gadolinium tantalate composite ceramic block material prepared in example 1, wherein fig. 1 and 2 are X-ray diffraction diagrams of the gadolinium zirconate and gadolinium tantalate powder materials obtained by the XRD test, respectively, and it can be seen from fig. 1 and 2 that both gadolinium zirconate and gadolinium tantalate powder have a single phase structure and no other heterogeneous phase; fig. 3 is an X-ray diffraction pattern of the gadolinium zirconate/gadolinium tantalate composite ceramic bulk material obtained by XRD test, and as can be seen from fig. 3, the XRD test only detects a diffraction peak of gadolinium zirconate, and does not detect a diffraction peak of gadolinium tantalate.
The gadolinium zirconate/gadolinium tantalate composite ceramic block material prepared in example 1 was used to perform thermal diffusivity and thermal expansion coefficient tests, and the thermal conductivity (as shown in FIG. 4) and the thermal expansion coefficient (as shown in FIG. 5) were analytically calculated to be 0.969W/(m.K) at 800 ℃, which is 30.288% lower than the thermal conductivity of pure gadolinium zirconate ceramic material mentioned in the published patent, and the thermal expansion coefficient is 11.741 × 10 -6 K -1 The thermal expansion coefficient of the pure gadolinium zirconate ceramic material is 10.400 x 10 which is higher than that of the pure gadolinium zirconate ceramic material mentioned in the published patent -6 K -1 。
Example 2
The embodiment of the invention provides a novel gadolinium zirconate/gadolinium tantalate composite ceramic material with high temperature resistance, low thermal conductivity and high thermal expansion coefficient and a preparation method thereof, and the preparation method specifically comprises the following steps:
weighing 12.784g of prepared gadolinium zirconate powder material and 3.616g of prepared gadolinium tantalate powder material, pouring 20 ml of absolute ethyl alcohol, mixing, placing in a planetary ball mill for ball milling (ball milling rotating speed is 120r/min, ball milling time is 12 h), drying the ball-milled suspension at room temperature for 20h, sieving with a 200-mesh sieve to obtain powder, placing the obtained powder in a die with the diameter of 15mm for compression molding, wherein the pressure is 30Mpa, and the pressure holding time is 1min. And then placing the obtained molded original sheet into a high-temperature furnace, and preserving heat for 6 hours at 1500 ℃ in the air atmosphere to obtain the gadolinium zirconate/gadolinium tantalate composite ceramic material.
An XRD test is performed on the gadolinium tantalate composite ceramic bulk material prepared in example 2, fig. 3 is an X-ray diffraction pattern of the gadolinium zirconate/gadolinium tantalate composite ceramic bulk material obtained by the XRD test, and as can be seen from fig. 3, the XRD test only detects a diffraction peak of gadolinium zirconate and does not detect a diffraction peak of gadolinium tantalate. The gadolinium zirconate/gadolinium tantalate composite ceramic block material prepared in example 2 was used to perform thermal diffusivity and thermal expansion coefficient tests, and the thermal conductivity (as shown in FIG. 4) and the thermal expansion coefficient (as shown in FIG. 5) were analytically calculated to be 0.921W/(m.K) at 800 ℃, which is 33.741% lower than the thermal conductivity of the pure gadolinium zirconate ceramic material mentioned in the published patent, and the thermal expansion coefficient is 10.473 × 10 -6 K -1 Higher than the thermal expansion coefficient 10.400 x 10 of pure gadolinium zirconate ceramic material mentioned in the published patent -6 K -1 。
Example 3
The embodiment of the invention provides a novel gadolinium zirconate/gadolinium tantalate composite ceramic material with high temperature resistance, low thermal conductivity and high thermal expansion coefficient and a preparation method thereof, and the preparation method specifically comprises the following steps:
weighing prepared gadolinium zirconate powder material 9.141g and gadolinium tantalate powder material 6.029g, pouring the mixture into anhydrous ethanol of 200ml, mixing, placing the mixture into a planetary ball mill for ball milling (ball milling rotating speed is 120r/min, ball milling time is 13 h), drying the ball-milled suspension at room temperature for 20h, sieving the suspension with a 200-mesh sieve to obtain powder, placing the powder into a mold with the diameter of 15mm, and performing compression molding under the pressure of 30Mpa and the pressure maintaining time of 1min. And then placing the formed original sheet into a high-temperature furnace, and preserving heat for 6h at 1500 ℃ in the air atmosphere to obtain the gadolinium zirconate/gadolinium tantalate composite ceramic material.
An XRD test is performed on the gadolinium tantalate composite ceramic bulk material prepared in example 3, fig. 3 is an X-ray diffraction pattern of the gadolinium zirconate/gadolinium tantalate composite ceramic bulk material obtained by the XRD test, and it can be seen from fig. 3 that the diffraction peak detected by the XRD test is mainly gadolinium zirconate and the diffraction peak of gadolinium tantalate is very weak.
The gadolinium zirconate/gadolinium tantalate composite ceramic block material prepared in example 3 was used to perform thermal diffusivity and thermal expansion coefficient tests, and the thermal conductivity (shown in fig. 4) and the thermal expansion coefficient (shown in fig. 5) were analytically calculated to be 0.920W/(m.k) at 800 ℃, which is 33.813% lower than that of the gadolinium zirconate ceramic material pure mentioned in the published patent, and to be 11.014 × 10 -6 K -1 Higher than the thermal expansion coefficient 10.400 x 10 of pure gadolinium zirconate ceramic material mentioned in the published patent -6 K -1 。
The thermal conductivity at 800 ℃ and the coefficient of thermal expansion at 1400 ℃ in each of the above examples and the published patent are shown in table 1.
TABLE 1
The technical features or mutual combinations between the technical features described in the above embodiments should not be considered as isolated, and they may be combined with each other to achieve a better technical effect. The examples are merely illustrative and should not be taken as limiting the scope of the invention.
Claims (9)
1. The gadolinium zirconate/gadolinium tantalate composite ceramic is characterized by having a chemical formula of (Gd) 2 Zr 2 O 7 ) 1-x /(GdTaO 4 ) x X is more than or equal to 0.1 and less than or equal to 0.9, namely the molar ratio of gadolinium zirconate to gadolinium tantalate is 9:1-1:9; the preparation method comprises the following steps:
1) Weighing gadolinium oxide and zirconium oxide according to a proportion to prepare gadolinium zirconate;
2) Mixing the weighed raw materials of gadolinium oxide and zirconium oxide in absolute ethyl alcohol, and then placing the mixture into a planetary ball mill for ball milling to ensure that the raw materials can be uniformly mixed;
3) Drying the mixed powder;
4) Pre-sintering the dried powder; cooling, taking out the pre-sintered sample, grinding, ball-milling and drying, and sintering the dried powder for the second time to obtain a gadolinium zirconate powder material;
5) Weighing gadolinium oxide and tantalum oxide according to a proportion to prepare gadolinium tantalate;
6) Ball-milling and drying the weighed raw materials of gadolinium oxide and tantalum oxide, and sintering the dried powder to obtain gadolinium tantalate;
7) Weighing gadolinium zirconate and gadolinium tantalate according to the proportion to prepare gadolinium zirconate/gadolinium tantalate composite ceramic;
8) Ball-milling, drying and sieving weighed gadolinium zirconate powder and gadolinium tantalate powder, placing the sieved powder in a mold for compaction, and then sintering;
in the step 8), the sieving refers to sieving by a 200-300-mesh sieve; the powder is pressed for 1min at the pressure maintaining pressure of 30-40 Mpa; the sintering temperature is 1400-1600 ℃, and the calcination time is 6h.
2. The preparation method of gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 1, comprising the following specific steps:
1) Weighing gadolinium oxide and zirconium oxide according to a proportion to prepare gadolinium zirconate;
2) Mixing the weighed raw materials of gadolinium oxide and zirconium oxide in absolute ethyl alcohol, and then placing the mixture into a planetary ball mill for ball milling to ensure that the raw materials can be uniformly mixed;
3) Drying the mixed powder;
4) Pre-sintering the dried powder; cooling, taking out the pre-sintered sample, grinding, ball-milling and drying, and sintering the dried powder for the second time to obtain a gadolinium zirconate powder material;
5) Weighing gadolinium oxide and tantalum oxide according to a proportion to prepare gadolinium tantalate;
6) Ball-milling and drying the weighed raw materials of gadolinium oxide and tantalum oxide, and sintering the dried powder to obtain gadolinium tantalate;
7) Weighing gadolinium zirconate and gadolinium tantalate according to the proportion to prepare gadolinium zirconate/gadolinium tantalate composite ceramic;
8) Ball-milling, drying and sieving the weighed gadolinium zirconate powder and gadolinium tantalate powder, placing the sieved powder in a die for compacting, and then sintering.
3. The method for preparing a gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 1), the molar ratio of gadolinium oxide to zirconium oxide is 1:2.
4. The method for preparing gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 2), the rotation speed of the ball mill is 120r/min, and the ball milling time is 12-13 h.
5. The method for preparing the gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 3), the drying temperature is room temperature, and the drying time is 15 to 24 hours.
6. The method for preparing the gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 4), the pre-sintering temperature is 1400 ℃, the secondary sintering temperature is 1400 ℃, and the sintering heat preservation time is 6 hours.
7. The method of claim 2, wherein in step 5), the molar ratio of the tantalum oxide to the gadolinium oxide is 1:1.
8. The method for preparing the gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 6), the sintering temperature is 1500 ℃ and the holding time is 6 hours.
9. The method for preparing the gadolinium zirconate/gadolinium tantalate composite ceramic according to claim 2, wherein in the step 7), the molar ratio of gadolinium zirconate to gadolinium tantalate is 9:1-1:9.
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